The email came at 3:47 PM on a Tuesday.

Ms. Orozco, please report to Dr. Keller's office immediately. Re: Project Helios compatibility results.

I'd been tested six months ago. Everyone at Helios was tested, standard company policy for working in the Supernatural Research Division. Most people got results within a week.

Mine had taken six months.

That usually meant one of two things: either the tests were inconclusive, or they'd found something they needed to verify.

I took the elevator to the executive floor. Dr. Keller's assistant waved me through without the usual appointment ritual.

That was alarming.

"Ms. Orozco." Dr. Keller stood as I entered, also alarming. She never stood for anyone. "Please, sit."

Her office was all white walls and chrome accents. The Helios sun logo dominated the wall behind her desk. Outside, glass walls faced the skyline, the city stretching toward a hazy horizon.

I sat.

"I'll be direct," she said. "Your genetic markers show a rare compatibility profile. One in approximately three million."

"Compatible with what?"

"With whom." She slid a tablet across the desk. "Roman Strand. Four hundred twenty-three years old. One of the oldest vampires in our database."

The image showed a man who appeared mid-thirties. Dark hair, light gray eyes, sharp features. He looked like money and danger wrapped in an expensive suit.

"I don't understand," I said. "I tested for compatibility months ago."

"The standard tests didn't catch it. Your markers are unusual. It took our lab significant time to identify the match." She folded her hands. "Mr. Strand is a candidate for our daylight serum trial. Are you familiar with the protocol?"

I was. Everyone in the division was. Helios had developed a serum that could allow vampires to tolerate sunlight, but only if they bonded with a genetically compatible human. The bond created some kind of physiological bridge that made the serum effective.

The trials had been stalled for years. Compatible matches were extraordinarily rare.

"He needs a bonded human for the serum to work," I said.

"Correct. And you're his only match in our database."

The tablet glowed between us. Roman Strand's image stared back, unblinking, as if the photograph itself had patience.

"What exactly are you asking me?"

"We're asking you to participate in a six-month clinical trial. You would need to live in our monitoring facility with Mr. Strand for the duration. Physical proximity is required for the bond to function."

"Live with a vampire for six months."

"A controlled environment with full security protocols. Your safety would be guaranteed."

I thought about my mother. Three rounds of chemo. Medical bills that multiplied while I slept. The insurance company's latest letter, sitting unopened on my kitchen counter.

"Compensation?"

Dr. Keller's smile was small and precise. "Five hundred thousand dollars upon completion of the trial. Plus full medical coverage for any family members for the duration."

I forgot how to swallow.

Five hundred thousand. Full medical coverage. Everything my mother needed. Everything I'd been working three jobs to provide.

"And if I decline?"

"Then the trial doesn't proceed. Mr. Strand remains nocturnal. You return to your regular duties." She paused. "No penalty, of course. This is entirely voluntary."

Voluntary. With half a million dollars hanging in the balance.

"I need to think about it."

"Of course. Take the weekend." She retrieved the tablet. "But I should mention, Mr. Strand has agreed to proceed, pending your consent. He's been waiting four hundred years for sunlight. I imagine he's eager to hear your decision."

I drove to the hospital instead of going home.

Mom was asleep when I arrived. The machines beeped their steady rhythm. Her face looked smaller every time I visited, like the illness was erasing her piece by piece.

The oncologist caught me in the hallway.

"The new treatment protocol is showing promise," he said. "But it's expensive. Your insurance..."

"Doesn't cover experimental treatments. I know."

"We can discuss payment plans."

Payment plans. For a treatment that cost more than I made in five years.

I stood by her bed until visiting hours ended. Watched her breathe. Counted the beeps.

Five hundred thousand dollars.

Full medical coverage.

All I had to do was live with a vampire.

I called Dr. Keller on Monday morning.

"Yes," I said. "I'm in."

"Excellent. Mr. Strand will be pleased." A pause. "You'll meet him tomorrow. I should warn you, he hasn't interacted voluntarily with a human in over two hundred years."

"Why not?"

"That's a question you'll have to ask him yourself."

She hung up before I could respond.

The Helios facility was in the corporate district. Top three floors of a building that looked like every other glass tower in the city. Nothing marked it as special.

Nothing marked it as the place where vampires came to try to walk in daylight.

Dr. Keller met me in the lobby.

"Before you meet him," she said as we walked to the elevator, "you should understand something. The bond you'll form isn't purely scientific. There are... side effects."

"What kind of side effects?"

"Emotional proximity. Shared dreams. A physical pull toward each other." She pressed the button for floor 47. "The bond was designed to make the serum effective. But it creates genuine connection, whether you intend it to or not."

"So I'll feel things for him."

"You'll feel things with him. Through him." The elevator rose. "It's not controllable. You should be prepared."

I thought about Roman Strand's picture. Four hundred years old. A face that seemed to see through photographs.

"I'm not planning to fall for a vampire, if that's what you're worried about."

Dr. Keller smiled. It seemed practiced.

"No one ever is."

The elevator opened.

I stepped out.

And the ground beneath my certainty gave way.